PLUMES AND FLUMING. 17 



and cause it to leak badly, or at least batter and wear it out more 

 rapidly than would be the case if the curve were more gradual. 

 More than this, there is always the increased danger of jams or blocks 

 occurring in the flume at such points. It is for this reason that shorter 

 boxes, which will more evenly graduate the curve, are desirable. 



There are no hard and fast rules that will correctly fit any and all 

 conditions, but in general on curves of from 6 to 10 degrees, the boxes 

 in a V-shaped flume should be "jointed" at least once in every 12 

 feet with corresponding spacing of bents and reinforced bracing. On 

 curves exceeding 10° and less than 15° the box should be jointed at 

 least once in every 8 feet of length, and on curves of more than 

 15° boxes should be jointed at least every 6 feet, with corresponding 

 spacing of bents and reinforced bracing in every case. 



As said before, but repeated now for the sake of emphasis, when- 

 ever it is possible without incurring too great or prohibitory expense, 

 very abrupt curvature should be avoided in flume construction, and 

 it will usually be found a wise policy to go to a considerable addi- 

 tional expense in excavation work or blasting out of rocks and ledges 

 in order to reduce curvature to a satisfactory degree. In every case 

 where extreme curvature is unavoidable the foundation footings upon 

 which the flume is supported should be carefully placed on very solid 

 material, in order to withstand the continued impact and jar of the 

 logs striking the sides of the flume; and the entire flume construction 

 should be strongly reinforced at such points, not only by shortening 

 the length of the boxes and placing the bents, side arms, and braces 

 closer together, but also, if trestling is necessary at such points, by 

 strongly reinforcing the trestle bracing, both "lateral" and "sway." 



Increase in height of sides of " V" on abrupt curves. — It is advisable 

 on abrupt curves to increase or raise the height of the V on the 

 outside of the curve, in order to cause the material being shipped to 

 drop back into the flume when it tries to "climb," as it always does 

 in such places, and thus prevent it getting on top of the side of the 

 flume and "riding" until it strikes some little projection or joint and 

 forms a "block" or "jam." (See PI. II.) On very sharp curves 

 it is usually advisable to raise both sides of the flume a little higher 

 than is necessary on tangents and on equable grades, in order to 

 retain the water in the flume, especially if there be a very abrupt 

 descent at the point of curvature, as is sometimes unavoidably the 

 case. The raising of the sides necessitates only the use of a longer 

 arm and additional height of the lining of the flume at such points. 



FEEDERS. 



Feeders constructed at various points along a flume line are 

 usually necessary in order to maintain the requisite amount of water 

 and to furnish a sufficient volume to operate a flume successfully on 



33346°— 14 3 



